The present invention relates to a soft magnetic film and a soft magnetic multilayer film for a core material of antennas for liquid crystal televisions, pulse motors, choke coils, transformers, inductors, noise filters, electromagnetic interference suppressers, magnetic impedance devices and magnetic heads, etc., a method of manufacturing the same, and a magnetic device having the same.
In recent years, development of information communication apparatuses such as personal computers, electronic organizers and portable telephones has rapidly been proceeding. Further, it is predicted that advanced information communication apparatuses that handle various data such as texts, sounds, still images and moving images will form a large market as a technology to support the advanced information (multimedia) society.
With such background, size reduction, thickness reduction, weight reduction and higher performance are required of information communication apparatuses. In the parts constituting information communication apparatuses, semiconductor devices have been reduced in size since an early time by being formed into thin-film parts or by integration because of the development of the LSI technology. However, size reduction and thickness reduction of magnetic devices by being formed into thin-film parts and by integration have not been attained yet.
Recently, a high-performance magnetic material has been required because of the demand for size reduction, thickness reduction and higher performance of magnetic devices such as antennas for liquid crystal televisions, pulse motors, choke coils, inductors, transformers, magnetic heads, impedance devices that eliminate noise and electromagnetic interference suppressers. For the magnetic core materials used for these magnetic devices, it is required that high saturation magnetization, an excellent soft magnetic property and a thin configuration be easily obtained. Therefore, the demand is increasing for the development of a thin-film magnetic device that is greatly required to be formed into a thin film and uses as the core material a soft magnetic thin film having high saturation magnetization.
Conventionally, as magnetic core materials for the above-mentioned uses, crystalline alloys such as Sendust, Permalloy and silicon steel, and Co-based amorphous alloys have been used. However, to achieve size reduction, thickness reduction and higher performance of magnetic devices, a soft magnetic film having higher saturation magnetization with both a high saturation magnetic flux density and an excellent soft magnetic property is required.
However, the above-mentioned crystalline alloys such as Sendust and Permalloy and Co-based amorphous alloys have a saturation magnetic flux density of as low as approximately 1 T although having an excellent soft magnetic property. Moreover, the crystalline alloy of silicon steel is inferior in soft magnetic property although having a high saturation magnetic flux density.
Research and development of an Fexe2x80x94N thin film as a material having a high saturation magnetic flux density of not less than 2 T are being made. For example, the Japanese Published Unexamined Patent Application, Pat. Publ. No. Sho 64-15907 and the Japanese Published Unexamined Patent Application, Pat. Publ. No. Hei 3-246913, disclose only Fexe2x80x94N thin films having insufficient coercive forces Hc which exceed 10 e (79.5775 A/m) and their soft magnetic property is not suitable for the above-mentioned demands for thin-film magnetic devices.
An object of the present invention is, in order to solve the above-mentioned problem, to provide higher-performance soft magnetic film and soft magnetic multilayer film with both a high saturation magnetic flux density and an excellent soft magnetic property, and a method of manufacturing the same .
Another object of the present invention is to realize size reduction, thickness reduction and higher performance of a magnetic device by employing a magnetic core material of an improved soft magnetic film or an improved soft magnetic multilayer film.
As a result of the inventor""s further intensive researches on the Fexe2x80x94N thin film, the below-mentioned fact was found. That is, a soft magnetic film of high saturation magnetization having an excellent soft magnetic property is obtained in an Fexe2x80x94N thin film having a high saturation magnetic flux density, on the condition that the main phases are xcex1-Fe and xcex3xe2x80x2-Fe4N, the crystal grain sizes of the xcex1-Fe phase and the xcex3xe2x80x2-Fe4N phase are made fine, the spacings of the lattice plane (110) of xcex1-Fe parallel to the film surface and the lattice plane (200) of xcex3xe2x80x2-Fe4N are expanded compared to those in the condition where there is no lattice strain, and the spacing of a lattice plane (111) of xcex3xe2x80x2-Fe4N is contracted compared to that in the condition where there is no lattice strain. The existence of the above-mentioned phases can be confirmed by the X-ray diffraction analysis.
A soft magnetic film according to the present invention is a soft magnetic film containing Fe and N and in which the main phases are xcex1-Fe and xcex3xe2x80x2-Fe4N, the mean grain diameters of the xcex1-Fe phase and the xcex3xe2x80x2-Fe4N phase are not more than 10 nm, the spacings of the lattice plane (110) of xcex1-Fe parallel to the film surface and the lattice plane (200) of xcex3xe2x80x2-Fe4N are expanded compared to those in the condition where there is no lattice strain and the spacing of the lattice plane (111) of xcex3xe2x80x2-Fe4N is contracted compared to that in the condition where there is no lattice strain.
As is apparent from the above-mentioned results of researches, according to this structure, a higher-performance soft magnetic film having both a high saturation magnetic flux density and an excellent soft magnetic property can be realized.
A soft magnetic film according to another aspect of the present invention has a double-layer structure where a soft magnetic thin film is formed on a Si thin film. The soft magnetic thin film contains Fe and N, and in the soft magnetic thin film, the main phases are xcex1-Fe and xcex3xe2x80x2-Fe4N, the mean grain diameters of the xcex1-Fe phase and the xcex3xe2x80x2-Fe4N phase are not more than 10 nm, the spacings of the lattice strain (110) of xcex1-Fe parallel to the film surface and the lattice plane (200) of xcex3xe2x80x2-Fe4N are expanded compared to those in the condition where there is no lattice strain, and the spacing of the lattice plane (111) of xcex3xe2x80x2-Fe4N is contracted compared to that in the condition where there is no lattice strain.
The inventor confirmed through experiment that the soft magnetic film has a more excellent soft magnetic property by forming the soft magnetic thin film on the Si thin film.
A soft magnetic multilayer film according to the present invention comprises a soft magnetic film and a non-magnetic film being alternately laminated. The soft magnetic film contains Fe and N, and in the soft magnetic film, the main phases are xcex1-Fe and xcex3xe2x80x2-Fe4N, the mean grain diameters of the xcex1-Fe phase and the xcex3xe2x80x2-Fe4N phase are not more than 10 nm, the spacings of the lattice plane (110) of xcex1-Fe parallel to the film surface and the lattice plane (200) of xcex3xe2x80x2-Fe4N are expanded compared to those in the condition where there is no lattice strain, and the spacing of the lattice plane (111) of xcex3xe2x80x2-Fe4N is contracted compared to that in the condition where there is no lattice strain.
In the soft magnetic multilayer film thus configured, the generation of eddy current due to magnetic induction between the laminated magnetic films can be suppressed even if the magnetic layers are increased in thickness, so that a magnetic core material being excellent in high-frequency characteristic can be provided.
A soft magnetic multilayer film according to another aspect of the present invention comprises a soft magnetic film and a non-magnetic film being alternately laminated. The soft magnetic film has a double-layer structure where a soft magnetic thin film is formed on a Si thin film. The soft magnetic thin film contains Fe and N, and in the soft magnetic thin film; the main phases of the film are xcex1-Fe and xcex3xe2x80x2-Fe4N; the mean grain diameters of the xcex1-Fe phase and the xcex3xe2x80x2-Fe4N phase are not more than 10 nm; the spacings of the lattice plane (110) of xcex1-Fe parallel to the film surface and the lattice plane (200) of xcex3xe2x80x2-Fe4N are expanded compared to those in the condition that there is no lattice strain; and the spacing of the lattice plane (111) of xcex3xe2x80x2-Fe4N is contracted compared to that in the condition that there is no lattice strain.
In the soft magnetic multilayer film thus configured, the generation of eddy current due to magnetic induction between the laminated magnetic films can be suppressed even if the magnetic layers are increased in thickness, so that a magnetic core material being excellent in high-frequency characteristic can be provided.
Moreover, the present invention provides a method of manufacturing the soft magnetic film or the soft magnetic multilayer film. The method comprises the step of forming the soft magnetic film or the soft magnetic multilayer film on a cooled substrate.
By thus forming the soft magnetic film or the soft magnetic multilayer film on the cooled substrate, only an xcex1-Fe microcrystal phase being lattice-expanded can be formed without any xcex3xe2x80x2-Fe4N phase in the condition immediately after the film formation.
Moreover, the present invention provides a method of manufacturing the soft magnetic film or the soft magnetic multilayer film. The method comprises the step of annealing the soft magnetic film or the soft magnetic multilayer film formed on the cooled substrate at a temperature of not more than 300xc2x0 C.
By thus annealing the soft magnetic film or the soft magnetic multilayer film formed on the cooled substrate at a temperature of not more than 300xc2x0 C., a soft magnetic film can be formed that has a configuration such that the spacings of the lattice plane (110) of xcex1-Fe parallel to the film surface and the lattice plane (200) of xcex3xe2x80x2-Fe4N are expanded compared to those in the condition where there is no lattice strain and the spacing of the lattice plane (111) of xcex3xe2x80x2-Fe4N is contracted compared to that in the condition where there is no lattice strain.
Moreover, it is desirable that a magnetic device including the soft magnetic film or the soft magnetic multilayer film in the magnetic core be one that is selected from among an antenna for a liquid crystal television, an electromagnetic interference suppresser, a noise filter, a pulse motor, a choke coil, a transformer, an inductor, a magnetic impedance device or a magnetic head. Due to excellent magnetic properties as described above, the soft magnetic film or the soft magnetic multilayer film can suitably be used for the achievement of size reduction, thickness reduction and higher performance of the selected magnetic device.
While the novel features of the invention are set forth particularity in the appended claims, the invention, both as to organization and content, will be better understood and appreciated, along with other objects and features thereof, from the following detailed description taken in conjunction with the drawings.